dt-bindings: display: Use OF graph schema

Now that we have a graph schema, rework the display related schemas to use
it. Mostly this is adding a reference to graph.yaml and dropping duplicate
parts from schemas.

In panel-common.yaml, 'ports' is dropped. Any binding using 'ports'
should be one with more than 1 port node, and the binding must define
what each port is.

Note that ti,sn65dsi86.yaml, ti,tfp410,yaml and toshiba,tc358768.yaml will
need further updates to use video-interfaces.yaml once that lands.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210104180724.2275098-1-robh@kernel.org
diff --git a/Documentation/devicetree/bindings/display/rockchip/rockchip,rk3066-hdmi.yaml b/Documentation/devicetree/bindings/display/rockchip/rockchip,rk3066-hdmi.yaml
index 4110d00..008c144 100644
--- a/Documentation/devicetree/bindings/display/rockchip/rockchip,rk3066-hdmi.yaml
+++ b/Documentation/devicetree/bindings/display/rockchip/rockchip,rk3066-hdmi.yaml
@@ -43,34 +43,24 @@
       This soc uses GRF regs to switch the HDMI TX input between vop0 and vop1.
 
   ports:
-    type: object
+    $ref: /schemas/graph.yaml#/properties/ports
 
     properties:
-      "#address-cells":
-        const: 1
-
-      "#size-cells":
-        const: 0
-
       port@0:
-        type: object
+        $ref: /schemas/graph.yaml#/properties/port
         description:
           Port node with two endpoints, numbered 0 and 1,
           connected respectively to vop0 and vop1.
 
       port@1:
-        type: object
+        $ref: /schemas/graph.yaml#/properties/port
         description:
           Port node with one endpoint connected to a hdmi-connector node.
 
     required:
-      - "#address-cells"
-      - "#size-cells"
       - port@0
       - port@1
 
-    additionalProperties: false
-
 required:
   - compatible
   - reg